I’m a Big Fan

You might be surprised to learn that most electric fans are in fact just miniature wind power generators running in reverse. Electrical energy enters the coils on the stator, which causes a fluctuation in magnetic field, which then exerts a force on the magnets, causing the rotor to spin. The spinning rotor turns the turbine, which converts the rotating mechanical energy into wind.

If you’re interested, you can find all kinds of projects on the Internet that show you how to turn old electric fans into miniature generators.

Conclusion

So now you know how hydroelectric generators (and all generators) work. Anytime you see a mechanical device generating electricity, be it via wind, steam, coal, or river power, there's a pretty good chance that these same steps are involved.